1. Field of the Invention
This invention relates to static induction apparatus, such as transformers, reactors, etc., and, more particularly, to a type of static induction apparatus provided with an improved noise reducing structure.
2. Description of the Prior Art
Generally, as fast-growing urban communities encroach upon the rural districts, housing for the growing number of urban workers tends to be located close to a substation, and a demand for reducing the noise generated by a static induction apparatus arises. Almost all the noises generated by a static induction apparatus are caused by vibration produced in the iron core of the apparatus and radiated into the atmosphere from the vessel after being transmitted through the bottom plate and insulating oil in the transformer. In one known method for reducing the noise, a sound reducing shed is built of conrete and iron sheets and used for reducing noise. Some disadvantages are associated with this method. For example, the area in which the equipment is installed increases, the cost rises and the period for carrying out work is prolonged.
In another known method, for reducing noise production by the side plates of a vessel, a frame formed of rubber or other resilient material is mounted at the peripheral end of each of reinforcing support members for supporting a sound insulating panel. When this method is used, there is the disadvantage that vibration is transmitted from the reinforcing support members to the sound insulating panel and the sound absorbing performance is reduced, because the spring constant of the resilient material cannot be sufficiently lowered due to limitations placed by the static displacement and the earthquake resisting performance of the sound insulating panel, although the transmission loss of the sound insulating panel itself is sufficiently large. When insulation rubber is used as resilient material, this material raises problems with regard to its weatherproof properties, reliability in performance, and cost.